1. Field of the Invention
The present invention relates to a process for agglomerating polymeric particulates in an aqueous latex, and more particularly relates to use in combination an organic acid and an organic anhydride to facilitate agglomeration of rubber particles in an aqueous latex.
2. Description of Related Art
Direct polymerization of diene monomers to large diameter rubber particles is typically a slow process via emulsion polymerization. Large rubber particles are desirable however in the production of ABS (acrylonitrile-butadiene-styrene) resin to produce resin exhibiting enhanced levels of impact strength. Chemical agglomeration processes exist for the production of large rubber particles from small rubber particles. These chemical agglomeration processes have in the past involved the addition of water soluble organic acids or water soluble organic anhydrides to facilitate agglomeration of the rubber particles. It has been discovered however that acid agglomeration and anhydride agglomeration of small rubber particles in an aqueous latex into large rubber particles in an aqueous latex can result in the formation of substantial amounts of coagulum (for example&gt;than 2% by weight) based on the total weight of rubber which is undesirable in the rubber phase of ABS resins because big masses of rubber (coagulum) can adversely affect the appearance and physical properties of the ABS resin or create production issues. A prior agglomeration process is set out in Dalton U.S. Pat. No. 3,558,541 issued Jan. 26, 1971 and is incorporated herein by reference.
Accordingly, it is desired to have an agglomeration process for agglomerating small rubber particles into large-size rubber particles without the formation of substantial amounts of coagulum.